Process for improving characteristics of a polyamide

Abstract

A process for improving characteristics such as, whiteness retention, degradation, and dyeability of a polyamide by contacting the polyamide with thiocyanate. A polyamide produced by the process has improved dyed color depth, dyed color uniformity, hue, elimination of light dyeing ends, protection of dye sites from degradation, protection from UV degradation, reduced yellowing or oxidation, and/or resistance to loss of dyeability.

What is claimed is:  
     
       1. A process for improving characteristics of a polyamide having X gram equivalents of amine end groups per 1,000 kg of polyamide, comprising contacting the polyamide or a salt useful to form the polyamide, prior to dyeing or other treatment that makes at least a portion of the amine end groups unavailable for subsequent dyeing, with a thiocyanate or reagent that provides thiocyanate, such that the polyamide after contacting or the polyamide formed from the salt contains Y gram equivalents of thiocyanate groups that protect the amine end groups, such that about 0.001<Y/X<about 1.5. 
     
     
       2. A process as claimed in claim  1 , such that 0.001<Y/X<1.1. 
     
     
       3. A process as claimed in claim  1 , wherein the contacting comprises contacting a polyamide, wherein the polyamide is in the form of flake, granules, molded articles, film, fiber, staple fiber, continuous filament tow, continuous filament yarn, fabric, garment, carpet or other articles. 
     
     
       4. A process as claimed in claim  1 , wherein the polyamide or the salt comprises one or more nylons or nylon salts. 
     
     
       5. A process as claimed in claim  1 , wherein the thiocyanate is selected from the group consisting of potassium, sodium, lithium, zinc, copper, and ammonium thiocyanates. 
     
     
       6. A process as claimed in claim  1 , further comprising after the contacting, scouring or rinsing the polyamide or the polyamide formed from the salt to remove excess thiocyanate not incorporated into the polyamide or salt. 
     
     
       7. A process as claimed in claim  1 , wherein the polyamide or polyamide formed from the salt is stabilized by exposure to heat after the contacting. 
     
     
       8. A process as claimed in claim  1 , further comprising after the contacting, dyeing the polyamide or a polyamide formed from the salt. 
     
     
       9. A process as claimed in claim  1 , wherein the contacting comprises applying the thiocyanate as a finish to a polyamide, wherein the polyamide is a filament comprising polyamide. 
     
     
       10. A process as claimed in claim  1 , wherein the contacting comprises applying the thiocyanate by padding to a polyamide, wherein the polyamide comprises a fabric comprising the polyamide. 
     
     
       11. A process as claimed in claim  1 , wherein the polyamide salt is contacted with the thiocyanate. 
     
     
       12. A polyamide produced by the process of claim  1 . 
     
     
       13. A polyamide having improved characteristics, wherein the polyamide contains terminal amine dye sites protected by thiocyanate groups. 
     
     
       14. A composition comprising a polyamide salt solution and a thiocyanate. 
     
     
       15. A process for improving characteristics of a polyamide, comprising contacting a polyamide having amine end groups with a thiocyanate, such that the polyamide after contacting contains up to about a stoichiometric amount of thiocyanate group based on the amine groups. 
     
     
       16. A process for improving dyeability characteristics of a polyamide, comprising contacting a polyamide prior to heat-setting or dyeing, with an amount of thiocyanate effective to protect dye-sites of the polyamide. 
     
     
       17. A process for improving characteristics of a polyamide, comprising contacting a polyamide salt with a thiocyanate, and polymerizing the salt to form a polyamide. 
     
     
       18. A process for improving characteristics of a polyamide fiber, yarn, film, tow, fabric, molded article, or garment comprising contacting the fiber, yarn, film, tow, fabric, molded article, carpet, garment or other article prior to any dyeing or other treatment that makes the amine end groups unavailable for subsequent dyeing, with a thiocyanate. 
     
     
       19. A polyamide fiber, yarn, film, tow, fabric, molded article, carpet, garment, or other article produced according to claim  18 . 
     
     
       20. A process as claimed in claim  1 , wherein the thiocyanate is an organic thiocyanate.